Diffusion refrigerating machine



April 4, 1939. G MA|UR| 2,153,020

DIFFUS ION REFRIGERATING MACHINE Filed July 3, 1937 4 Sheets-sheet lfwwwfor UIDD MHIURI FITTORNEY April 4, 1939. G MA|UR| 2,153,020

I DIFFUSION REFRIGERATING MACHIVNE Filed July 3, 1957 4 Sheets-Sheet 2 IL i II I I I 1 GUIDO MFHURI FTTTORNEY April 4, G. 'MA|UR| 2,153,020

DIFFUSION REFRIGERATIiIG MACHINE Filed Jul 3, 1937 4 Sheets-Sheet s I I?m I f 1 x"; El Z, 'l f I I Fang V 6- I 7 a ,fiwenfor Guuoo MHIURIFITTORNEY April 4,- 1939. G, MAIUR] 2,153,020

DIFFUSION REFRIGERATING MACHINE Filed July 3, 1937 4 Sheets-Sheet 4fvweniar GUI 00 MPH URI HTTORNE Patented Apr, 4, 1939 Application July3, 1937, Serial No. 151,777 In Great Britain April 30, 1937 18 Claims.

This invention relates to diffusion refrigerating machines wherein coldis produced over a wide range of temperatures, preferably-extending froma very low temperature, by the evaporation of a refrigerant underincreasing partial pressure.

By diffusion refrigerating machine is meant an absorption or resorptionrefrigerating machine wherein the refrigerant evaporates into and isabsorbed from an atmosphere of inert gas.

Now to obtain a wide range of partial pressures of the evaporatingrefrigerant, extending from a low minimum partial pressure, and thus toobtain a wide range of refrigerating temperatures, the quantity of inertgas present in the evaporator of the diffusion refrigerating machinemust be so limited that the maximum partial pressure of the refrigerantat least closely approaches the total pressure in the evaporator. A lowminimum partial pressure of the refrigerant can be obtained by the inertgasbeing suppliedto theevaporator substantially freed from refrigerantvapour in the absorber. A low minimum temperature of evaporation can beensured by precooling to the minimum temperature, the'inert gas, freedfrom refrigerant vapour, and also the liquidrefrigerant prior toadmiss'ion of the gasto the liquid refrigerant in the evaporator, sothat the initialevaporation under the minimum partial pressure with theaccompanying low temperature can be preserved against being increased bythe large quantity of refrigerant which would have to evaporated, merelyto cool the arriving inert gas and liquid refrigerant.

Now the chief purpose of a refrigerating machine producing cold. along arange of "temperatures, as distinguished from at approximately a singletemperature, is to cool fluids by contra- 4( flow heat-exchange with theevaporating refrigerant. The production of cold should therefore be asuniform in quantity as possible along the range of temperatures, as thequantity of contra-flowing fluid to be cooled must obviously remainuniform throughout'the range of heat-exchange.

Now with the same quantity of inert gas flowing from one end to theother of the evaporator and the mixture cigars ,and refrigerant vapourincreasing in volume by evaporation of refrigerant, the quantity'ofrefrigerant which must be evaporated to increase the temperature ofevapo ration by 1 C. by a corresponding increase of the partialpressure, is very small at low temperatures but increases rapidly withthe temperature.

This increase of quantity of refrigerant evaporated to produce avariation of temperature of 1 C. depends also on the total pressure ofinert gas plus refrigerant vapour in the evaporator.

A numerical example using ammonia as the 5 refrigerant shows that toincrease the temperature from C. to 74 C. if one cubic metre of inertgas mixture is circulating per unit of time 5.66 grammes of ammonia haveto be evaporated when the total pressure is 5 atmospheres o absolute. Atthe same total pressure, 63 grammes must be evaporated per cubic metreof gas mixture circulating, to increase the temperature of evaporationfrom --30 C. to -29 C.

. With a total pressure of 2 atmospheres abso- 15 late, to increase thetemperature from -.-75 C.

to --74 C., 5.88 grammes of ammonia must evaporate per cubic metre'ofgas mixture circulating, and to increase the temperature from -30 C. to.-29 0., 127 grammes of ammonia must evap- 20 orate.

As it is necessary to evaporate the. same amount .of ammonia in order tocool a. given amount of fluid one degree centigrade independently of thetemperature, it is evident that a volume of gas 25 mixture in inverseproportion to the above given weights of ammonia evaporated should becirculated to keep theamount of cold produced substantially uniformthroughout the range of temperatures. 30

' For instance to evaporate grammes of ammonia per hour per each degree0. of variation of temperature (which would allow the cooling by onedegree C. of 10 cubic metres of fluid such as nitrogen or'air per hour)the volume of gas mix- 35 ture to be circulated at various parts of theevaporator should be, with a total pressure of 5 atmospheres absolute,1.59 cubic metres from 30 C. to --29 C. and 17.6 cubic metres from 75"-C. to 74 C. The volume of gas mixture 40 to be circulated should be witha total pressure of -2 atmospheres absolute, 0.79 cubic metre from -30C. to -29 C. and 17.0 cubic metres from -75 C. to -'74 C.

The object of the present invention is to render 45 substantiallyuniform the production of cold along a wide range of temperatures in adiffusion refrigerating machine. This is efl'e'cted, according to theinvention, by progressively divertin'g inert gas out of the evaporatorof a dif- 50 fusion refrigerating machine, at a ratepermitting a uniformrate of evaporation per degree of increase of temperature throughout theflow of the inert gas within the evaporator. In otherwords, sufficientinert gas is progressively ex- 55 tracted from the evaporator to reducethe amount of inert gas remaining therein at all parts of r theevaporator traversed by inert gas, so that whereby the correctlyproportioned progressive-' a uniform rate of evaporation of refrigerantalong the evaporator will produce a uniform rate increase of the partialpressure and temperature.

The inert gas is progressively extracted from the evaporator by leakingthrough a series of holes into a space connected to the absorber and ata slightly lower pressure than the evaporator.

These-holes are preferably arranged in a helical row in the wall of acylindrical evaporator,

ly decreasing leakage of inert gas can be predetermined by the steepnessof pitch of the row and size andcloseness of the holes.

The decrease of inert gas circulation necessary to keep constantthegradient of temperature is much larger at low. temperatures than athigher temperatures and for this reason the holes must be closertogether or larger or both at the colder end of the evaporator andprogressively at an increasing distance apart or smaller or both towardsthe less cold end.

The total pressure in the evaporator may be so limited that the maximumtemperature of evaporation of the refrigerant is considerably lower thanatmospheric temperature. For example, using ammonia as the refrigerant,the total pressure may be two atmospheres absolute.

-At the lower end of the range of partial presat a temperature of -20'C. Incidentally at this part of the evaporator very little inert gas ifany may be present as all or nearly all may have been already diverted,but this does not aflect the upper limitation of temperature as thelatter depends upon the total pressure whether due to gas or vapour orboth.

Asthe primary use of the machine is to cool fluids and for instance incooling compressed air for obtaining liquid air or oxygen, the coolingis effected from atmospheric temperature, a suitable excess of coldshould in such case be produced at 20 C. to cool the air from say +20 C.to say -l9 0. Below -19 C. the c001 ing is effected with but slightdifference of temperature sufficient merely to effect heat transmission,by the cold produced along the range of temperatures from --20 C. to -71C. To produce the excess of cold at -20i C. evaporation of the ammoniais continued by ebullitionunder the total pressure of 2 atmospheresabsolute,

like in refrigerating machines having no inert,

erant from the inert gas which enters the absorber cold from theevaporator.

The diverted inert gas mixture is conducted in heat-exchange with thegas left in the evap- The weak liquor is thus rendered capable ofabsorbing'more refrigaisaoso orator, and may be led also inheat-exchange proximity with the gas coming from the absorber. Thediverted gas mixture is sent to a convenient part of the absorber. Itmay be advantageous in some cases to keep separated the diverted inertgas mixtures of various proportions of gas and vapour and to conduct thevarious parts of the diverted gas mixture into parts of the absorberwhere the composition is similar.

constructional embodiments of diffusion refrigerating machines accordingto the invention are illustrated by way of example on the accompanyingdrawings, in which:

Fig. 1 is an elevation partly in section of an entire diffusionrefrigerating machine.

Fig. 2 is a sectional elevation of the evaporator of the machine, on alarger scale than Fig. 1.

Fig. 3 is a sectional elevation of the absorber of the machine, on alarger scale than Fig. 1.

"Fig. 4 is a sectional elevation of a modified machine.

Referring more particularly to Figs. 1 to 3:

a. is the boiler of the refrigerating machine, heated by a gas burner b.

a is a horizontal cylindrical portion of the boiler a located at thelevel of and providing a wide expanse of upper surface of the liquid inthe boiler. v

c is a rectifier extending upwards from the boiler a and cooled by aninternal pipe coil to and from which water flows by connections c 0.

d is a condenser connected to the rectifier e.

e is an absorber.

j is an evaporator.

a is a pump delivering rich liquor, coming from the absorber e by a pipe9 to one end of the outer tube It of a coiled tube heat-exchanger. .theother end of which latter is connected to the horizontal portion a ofthe boiler, by a pipe h Weak liquor leaves the boiler a by a pipe iwhich extends within the coiled outertube h of the heat-exchanger, fromwhence the pipe i passes provided with a stop cock F, to a precooler inthe evaporator f, and thence the weak liquor passes to the absorber e,as described hereinafter.

The condenser d delivers liquid refrigerant, for instance ammonia, tothe evaporator f by a pipe d Before entering the evaporating space inthe evaporator j, the liquid refrigerant traverses a pipe coil 1 in theupper portion of the evaporator f wherein the liquid refrigerant iscooled approximately to the temperature reigning in such upper part ofthe evaporator. .The cooled liquid refrigerant is delivered, by a pipeIn connected to the pipe coil j and branching into two branches k and Itprovided with stop cocks It k into the evaporator ,f at two levels.

M, the liquid refrigerant'overflows, from an an- I nular trough I, anannular weir l straddled by a wire gauze wick l, which distributes theliquid refrigerant on to pipe coils beneath. In the.

upper portion of the evaporator the respective pipe coils are thealready mentioned pipe coil 1 wherein the liquidrefrigerant is cooled,and a second pipe coil m intercoiled therewith and connected to the weakliquor supply piper;

Owing to being cooled in the coil m before entering the absorber e, theweak liquor more readily absorbs refrigerant vapour coming from theevaporator I by a pipe f connecting the top of fie evaporator to theupper end of the absor r e.

The top of the absorber e is connected by a pipe e to a pipe coil 11extending downwards within the evaporator f and opening into theevaporator at the bottom thereof. I I I Above the pipe coil n is anannular trough 0,

into which the branch pipe It delivers liquid refrigerant to overflow aweir o straddled by a wire gauze wick on to the pipe coil n. I

The absorber e and evaporator f are charged with inert gas, for instancenitrogen, which is driven by a fan e from the absorber 6 along the pipe8 and pipe 0011 n into the evaporator f. The inert gas becomesrefrigerated by the refrigerant evaporating on the pipe coil n, beforebeing discharged into the lower end of the evaporator f.

' The lower portion of the evaporator f issur- I rounded by a jacket 9.with whichthe interior of the evaporator f communicates by a helical rowof holes q. The jacket pl is connected by a pipe 1' with an annularspace between the wall of the absorber e and, a cylindrical partition sin the absorber c. This annular space is closed at the top by the baseof an annular trough t at the top of the absorber e and is open at thelower end whereby the annular space communicates with the space withinthe cylindrical partition .9.

Inside the absorber e, a sheet metal fairing or core 11. provides anannular space surrounded by the cylindrical partition s and in which apipe coil '0, traversed by cooling water, extends beneath the trough t.The trough t is bordered by an annular weir t straddled by a wire gauzewick t over which weak liquor flows and is distributed over the pipecoil 11.

Evaporation takes place at the lower end of the evaporator f where theinert gas is delivered, precooled, by the pipe coil n, under the minimumpartial pressure and therefore at the minimum temperature. Evaporationproceeds upwards under progressively increasing partial pressure, andtherefore at progressively increasing temperatures, as the gas ascendsin the evaporator. In ascending in theevaporator f the inert gas mixedwith the refrigerant vapour progressively flows out through the holes qinto the jacket :1 and thence directly to the absorber e. The dis--tance between successive holes q increases from the lower to the upperend of the helical row, such that the inert gas mixture leaves theevaporator ata rate which causes the amount of refrigerant evaporated tobe uniform as the partial pressure and temperature increase.

At the upper end of the row of holes q all or most ofthe inert gas haspassed from the evapo-* rator i into the jacket p, and the evaporationproceeds by ebullition at the total pressure and therefore at themaximum temperature in the part of the evaporator 1 between thetermination of the row of holes q and the lower trough 0. Here an excessof cold is produced at the maximum temperature and is utilised ashereinafter described.

Between the two troughs l and o in the evapo rator j, evaporation alsoproceeds at the total pressure and maximum temperature, and, as abovedescribed, is utilised to precool the weak liquor in the pipe coil m andthe liquid refrigerant in the pipe coil ;i.

w are two pipe coils extending intercoiled with the inert gas pipe coiln downwards beneath the lower trough o in the evaporator "f. Fluid to becooled, such as nitrogen in an oxygen plant, is passed in paralleldownwards through the two pipe coils w, and thus becomes cooled by therefrigerant evaporating in the evaporator beneath the lower trough o. I

The total pressure in the evaporator ,f is kept low, for instancetwoatmospheres absolute, and in consequence the maximum temperature ofevaporation of ammonia is below atmospheric temperature, namely for twoatmospheres absolute, is -20 C. The fluid has, however, to be cooledfrom atmospheric temperature for instance +20 C. to for instance 19 C.before being cooled by the refrigerant evaporating at, a range oftemperatures under the range of partial pressures reigning in the lower,gas traversed, portion of the evaporator. This first portion of thecooling is efiected by the excess of cold produced, as above described,at the maximum evaporation temperature under the totalpressure.

The evaporated refrigerant not removed by the inert gas which hasescaped through the holes q, passes, together with any remaining inertgas, from the top of the evaporator j into the top of the absorber e bythe pipe I interconnecting the absorber e and evaporator f. Theresistance to flow in this pipe 1 causes a slight excess of pressure inthe evaporator ,f promoting the leakage of inert gas through theholes q.

Any unevaporated liquid refrigerant drains from the bottom of theevaporator f by a pipe a into a jacket :11 surrounding the rich liquorpipe 9 Some of the refrigerant boils in this jacket 11 and by thebubbles of vapour so produced the remainder of the liquid refrigerant israised up a pipe 2 into the bottom of the absorber e where it mixes withand is absorbed in the rich liquor.

x is a non-return valve in the pipe :2:.

The cooling of the rich liquor effected by the refrigerant in the jacket3/, reduces the liability of the suction of the pump g causingevaporation from the rich liquor.

The inert gas does not serve to equalise the pressure thoughout themachine. The pressure in the boiler and condenser is greater than thepressure in the absorber and evaporator and the rich liquor is raised tothe boiler pressure by the pump a. For instance with ammonia a boilerand condenser pressure of 9 atmospheres absolute is required to effectcondensation with cooling water at 20 C.

The modified construction of diffusion refrigerating machine shown inFig. 4 is intended to be used in cascade with the machine shown in Figs.1 to 3, in order to extend the range of temperatures to a lower minimumtemperature, for instance to -100 C. For this purpose, a refrigerantsuch as ethane and an absorption liquid such as butane, or toluol, orethylene as the-refrigerant with dichlorethylene as the absorbent, whichwill not freeze at the minimum temperature are employed. Also, as usualin cascade refrigeration, evaporating liquid refrigerant from the highertemperature refrigerating machine, such as ammonia, is used to cool tothe condensing temperature, which is below atmospheric temperature, therefrigerant, such as ethane in the lower temperature refrigeratingmachine, and also to cool the absorber.

The machine however can be used as an independent refrigerating machinewith a refrigerant condensing at atmospheric temperature.

a is the boiler wherein liquor is heated'by steam generated in a chambera by a gas burner b. c isthe rectifier. d is the condenser, cooled byammonia evaporating in a pipe I.

The evaporator ,f is superposed on and is connected to the absorber e,by a tubular neck 2.

In this neck 2 the cold inert gas mixture descends from the evaporatorfin contra-flow heatexchange with inert gas, freed from refrigerantascending in pipes 3, from the absorber e to the evaporator ,f.

Liquid refrigerant passes by a pipe d to a cooling coil 7' in theevaporator j and thence by a pipe is with stop cock k to an annulartrough at the top of the evaporator f.

The refrigerant descends over a weir o and wick 0 on to the pipe coils7' and w, wherein respectively liquid refrigerant is precooled andextraneous fluid is cooled.

A cylindrical partition 4 closed'at the upper end extends upwards fromthe neck 2. This partition 4 is formed with a helical row of holes q,through which inert gas mixed with refrigerant vapour progressivelypasses out of the annular space wherein evaporation of the descendingrefrigerant takes place. This progressive escape of gas mixture isarranged to render substantially uniform the production of cold alongthe range of increasing partial pressures and temperatures in theevaporator, as already explained.

Below the holes q the refrigerant boils at the total pressure and thevapour enters the neck 2 through openings 5 in the partition 4.

The inert gas mixture passes to the bottom of the absorber e along theinterior of a cylindrical partition 6 extending downwards from the neck2.

Weak liquor is delivered into an annular trough t at the top of theannular space surrounding the cylindrical partition 6 in the absorber e.The weak liquor overflows a weir t straddled by a wick t which deliversthe liquor on to a cooling pipe coil 12 traversed by a cooling liquid,such as liquid ammonia if a cascade machine, or, if not, by coolingwater.

The liquor enriched by absorbing refrigerant from the gas mixture,passes by a pipe 9 to a pump g which forces it through the outer memberh of a heat-exchanger coil to a pipe h which delivers it into the boilera.

I claim:

1. In a diffusion refrigerating machine, a boiler, a refrigerantreceiver connected to said boiler, an evaporator charged with inert gasand connected to said refrigerant receiver and having means providingprogressive outlet of inert gas from adjacent one end of and along saidevaporator, an absorber charged with inert gas and connected to saidboiler, an inlet conduit interconnecting said absorber and saidevaporator and providing circulation of said inert gas from saidabsorber to said end of said evaporator adjacent said progressive outletmeans, and an outlet conduit interconnecting said progressive outletmeans of said evaporator and said absorber and providing circulation ofsaid inert gas from said evaporator to said absorber.

2. In a diffusion refrigerating machine, a boiler, a refrigerantreceiver connected to said boiler, an evaporator charged with inert gasand connected to said refrigerant receiver and having means providingprogressive outlet of inert gas from adjacent one end of and along saidevaporator, an

absorber charged with inert gas and connected to said boiler, an inletconduit interconnecting said absorber and said evaporator and providingcirculation of said inert gas from said absorber to said end of saidevaporator adjacent said progressive outlet means, an outlet conduitinterconnecting said progressive outlet means of said evaporator andsaid absorber and providing circulation of said inert gas from saidevaporator to said absorber, and a second outlet conduit interconnectingsaid evaporator beyond said progressive outlet means and said absorber.

3. In a diffusion refrigerating machine, a boiler, a refrigerantreceiver connected to said boiler, an evaporator charged with inert gasand connected to said refrigerant receiver and having means providingprogressive outletv of inert gas from adjacent one end of and along saidevaporator, an absorber charged with inert gas and connected to saidboiler, an inlet conduit interconnecting said absorber and saidevaporator and providing circulation of said inert gas from saidabsorber to said end of said evaporator adjacent said progressive outletmeans and extending in contraflow heat-exchange proximity with inert gascirculating in said evaporator, and an outlet conduit interconnectingsaid progressive outlet means of said evaporator and said absorber andproviding circulation of said inert gas from said evaporator to saidabsorber.

4. In a diffusion refrigerating machine, a boiler, a refrigerantreceiver connected to said boiler, an evaporator charged with inert gasand connected to said refrigerant receiver and having means providingprogressive outlet of inert gas from adjacent one end of and along saidevaporator, an absorber charged with inert gas and connected to saidboiler, an inlet conduit interconnecting said absorber and saidevaporator and providing circulation of said inert gas from saidabsorber to said end of said evaporator adjacent said progressive outletmeans and extending in contra-flow heatexchange proximity with inert gascirculating in said evaporator, an outlet conduit interconnecting saidprogressive outlet means of said evaporator and said absorber andproviding circula tion of said inert gas from said evaporator to saidabsorber, and a second outlet conduit interconnecting said evaporatorbeyond said progressive outlet means and said absorber.

5. In a diffusion refrigerating machine, a boiler, a-refrigerantreceiver connected to said boiler, an evaporator charged with inert gasand having means providing progressive outlet of inert gas from adjacentone end of and along said evaporator, an absorber charged with inert gasand connected to said boiler, an inlet conduit inter' connecting saidabsorber and said evaporator and providing circulation of said inert gasfrom said absorber to said end of said evaporator adjacent saidprogressive outlet means, an outlet conduit interconnecting saidprogressive outlet means of said evaporator and said absorber andproviding circulation of said inert gas from said evaporator to saidabsorber, a second outlet conduit interconnecting said evaporator beyondsaid progressive outlet means and said absorber, and an inlet conduitinterconnecting said refrigerant receiver and said evaporator inheat-exchange proximity with refrigerant evaporating in said evaporatorbetween said second outlet conduit and said progressive outlet means.

6. In a diffusion refrigerating machine, a boiler, a refrigerantreceiver connected to said boiler, an evaporator charged with inert gasand having means providing progressive outlet of inert gas from adjacentone end of and along said evaporator, an absorber charged with inert gasand connected to said boiler, an inlet conduit interconnecting saidabsorber and said evaporator and 1 providing circulation of said inertgas from said absorber to said endof said evaporator adjacent saidprogressive outlet means and extending in contra-flow heat-exchangeproximity with inert gas circulating in said evaporator, an outletconduit interconnecting said progressive outlet means of said evaporatorand said absorber and providing circulation of said inert gas from saidevaporator to said absorber, a second outlet conduit interconnectingsaid evaporator beyond said progressive outlet means and saidabsorber,and an inlet conduit interconnecting said refrigerant receiver and saidevaporator in heat-exchange proximity with refrigerant evaporating insaid evaporator between said second outlet conduit and said progressiveoutlet means.

'1. In a diffusion refrigerating machine, a boiler, a refrigerantreceiver connected to said boiler, an evaporator charged with inert gasand connected to said refrigerant receiver and having'a series of holesextending from adjacent one end of and along said evaporator, anabsorber charged with inert gas and connected to said boiler, an inletconduit interconnecting said absorber and said evaporator and providingcirculation of said inert gas from said absorber to said end of saidevaporator adjacent said series of holes, and an outlet conduitinterconnecting said series of holes of said evaporator and saidabsorber and providing circulation of said inert gas from saidevaporator to said absorber.

8. In a difiusion refrigerating machine, a boiler, a refrigerantreceiver connected to said boiler, an evaporator charged with inert gasand connected to said refrigerant receiver and having a series of holesextending from adjacent one end of and along said evaporator, anabsorber charged with inert gas and connected to said boiler, an inletconduit interconnecting said absorber and said evaporator andprovidln'g-cir oulation of said inert gas from said absorber to said endof said evaporator adjacent said series of holes, an outlet conduitinterconnecting said series of holes of said evaporator and saidabsorber and providing circulation of said inert gas from saidevaporator to said absorber, and a second outlet conduit interconnectingsaid evaporator beyond said series of holes and said absorber.

9. In a diffusion refrigerating machine, a boiler, a refrigerantreceiver connected to said boiler, an evaporator charged with inert gasand connected to said refrigerant receiver and having a series of holesextending from adjacent one end of and along said evaporator, anabsorber charged with inert gas and connected to said boiler, an inletconduit interconnecting said absorber and said evaporator and providing.circulation of said inert gas from said absorber to said end of saidevaporator adjacent said series of holes and extending in contra-flowheat-exchange proximity with inert gas circulating in said evaporator,andan outlet conduit interconnecting said series of holes of saidevaporator and said absorber and providing circulation of said inert gasfrom said evaporator to said absorber, and a second outlet conduitinterconnecting said evaporator beyond said series of holes and saidabsorber.

10. In a diffusion refrigerating machine, a boiler, arefrigerantreceiver'connected to said boiler, an evaporator charged with inert gasand connected to said refrigerant receiver and having a series of holesextending from adjacent one end of and along said evaporator, anabsorber charged with inert gas and connected to said boiler, an inletconduit interconnecting said ohsorberand said evaporator andprovidingcirculation of said inert gas from said absorber to boiler, anevaporator charged with inert gas and having a series of holes extendingfrom adjacent one end of and along said evaporator, an absorber chargedwith inert gas and connected to said boiler, an inlet conduitinterconnecting said absorber and said evaporator and providingcirculation of said inert gas from said absorber to said end of saidevaporator adjacent said series of holes, an outlet conduitinterconnecting said series of holes of said evaporator and saidabsorber and providing circulation of said inert gas from saidevaporator to said absorber, a second outlet conduit interconnectingsaid evaporator beyond said series of holes and said absorber, and aninlet conduit interconnecting said refrigerant receiver and saidevaporator in heatexchange proximity with refrigerant evaporating insaid evaporator between said second outlet conduit and said ser es ofholes.

12. In a diffusion refrigerating machine, a

boiler, a refrigerant receiver connected to said boiler, an evaporatorcharged with inert gas and having a series of holes extending fromadjacent one end of and along said evaporator, an absorber charged withinert gas and connected to said boiler, an inlet conduit interconnectingsaid absorber and said evaporator and providing circulation of saidinert gas from said absorber to said end of said evaporator adjacentsaid series of holes and extending in contra-flow heatexchangeproximitywith inert gas circulating in said evaporator, an outlet conduitinterconnecting said series of holes of said evaporator and saidabsorber and providing circulation of said inert gas from saidevaporator to said absorber,

a second outlet conduit interconnecting said evaporator beyond saidseries of holes and said absorber, and an inlet conduit interconnectingsaid refrigerant receiver and said evaporator in heat-exchange proximitywith refrigerant evaporating in said evaporator between said secondoutlet conduit and said series of holes.

13. In a diffusion refrigerating machine, a;

' boiler, a refrigerant receiver connected to said boiler, an evaporatorconnected to said refrigerant receiver. an absorber connected to saidevaporator, a pump, a conduit conducting liquor from said absorber tosaid pump, a conduit conducting liquor from said pump to said, boiler, a

conduit conducting liquor from said boiler to 75 said absorber, and aconduit in heat-exchange proximity with said conduit conducting saidliquor to said pump and conducting to said absorber refrigerantdrainingfrom said evaporator.

15. In an absorption refrigerating machine. a boiler, a refrigerantreceiver connected to said boiler, an evaporator connected to saidrefrigerant receiver, an absorber connected to said evaporator, a pump,a conduit conducting liquor from said absorber to said pump, a conduitconducting liquor from said pump to said boiler, a conduit inheat-exchange proximity with refrigerant evaporating in said evaporatorand conducting liquor from said boiler to said absorber, and a conduitin heat-exchange proximity with said conduit conducting said liquor tosaid pump and conducting to said absorber refrigerant draining from saidevaporator.

16. A method of producing a range of temperatures in a diffusionrefrigerating machine and uniformly cooling a fluid byand along saidrange of temperatures, consisting in evaporating refrigerant underincreasing partial pressures of refrigerant in an inert gas,progressively decreasing the amount of said inertgas flowing past saidrefrigerant as said partial pressures increase,

' and passingsaid fluid in contra-flow heat-exchange proximity with saidinert gas wherein said refrigerant is evaporating under said increasingpartial pressures.

17. A method of producing a wide range of temperatures in a vdiflusionrefrigerating machine \and limiting the production of cold at thehigher-temperatures of said range of temperatures, consisting inprecooling by heat-exchange with refrigerant evaporating in said machineinert gas and refrigerant liquid in said machine prior to admission ofsaid inert gas to said refrigerant liquid, evaporating said refrigerantin said inert gas under partial pressures of refrigerant increasingapproximately to the total pressure of said inert gas and refrigerant,and

progressively diverting said inert gas from said refrigerant as saidpartial pressures increase.

18. A method of producing a wide range of temperatures in a diffusionrefrigerating machine and uniformly cooling a fluid by and along saidrange oftemperatures. consisting in precooling by heat-exchange withrefrigerant evapcrating in said machine inert gas and refrigerant liquidin said machine prior to admission of said inert gas. to saidrefrigerant liquid, evaporating said refrigerant in said inert gas underpartial pressures of refrigerant increasing approximately to the totalpressure of said inert gas and refrigerant, progressively diverting saidinert gas from said refrigerant as said partial pressures increase, andpassing said fluid in contra-flow heatexchange proximity with said inertgas within said refrigerant is evaporating under said increasing partialpressures.

GUIDO MAIURI.

